Whether you are a man or a mouse, or a rat come to that, drinking too much alcohol is bad for you. Many of us have observed at first or second hand the effects of ethanol on the central nervous system. Those effects are over a broader spectrum than we realize. One interaction is with the μ-opioid receptor giving a feel good effect from an increase in dopamine. A study by He and Whistler of U of California (1) has shown a downside to this in that a tolerance to morphine (the μ in μ-opioid) can result.
The study was carried out with a team of alcoholic rats. These were indulged with an open bar on Mondays, Wednesdays and Fridays when booze equivalent to 50/50 vodka/water was available. Plain water was always on tap as well, of course. On Tuesdays and Thursdays, they were on the wagon. Curiously, no mention was made of their drinking habits over weekends. I guess gentlemen wouldn’t ask about that, after all, they wouldn’t be working and would be on their own time.
The analgesic effect of morphine was checked on both teetotal and alcoholic rats by shining a heat lamp on their tails and measuring the time it took them to flick it out of the way. A maximum of 10 seconds was allowed so as not to produce damage for those enjoying a morphine high.
The first item of bad news for the alcoholic rats is that all that booze reduces the effect of morphine, so they felt the heat. The other item of bad news is that the primary therapeutic for mending alcoholics, naltrexone, is also blocked so they’d be going cold turkey for longer. However, that didn’t end up as their problem; their destiny was elsewhere.
